Apparatus and Process for the Separation of Solids and Liquids

ABSTRACT

A filter column apparatus comprising a filtration zone and a reslurry zone. These zones are separated by a barrier wall or are in substantial cooperation with each other. Also disclosed is a process for separating at least a portion of at least one substantially solid component from a solid-liquid stream comprising the substantially solid component and at least one substantially liquid component. Also disclosed is a process for forming a substantially solids containing packed bed. Also disclosed is a process for purifying paraxylene in a filtration zone.

FIELD OF THE INVENTION

This invention relates to filter column apparatuses and processes usefulfor separating solids and liquids.

BACKGROUND OF THE INVENTION

In many industrial chemical processes, various separation techniques areused to isolate one material from another. These separations can beliquid from liquid or liquid from solid. Two common separationmechanisms that can be useful for chemical processes, and in particular,aromatic hydrocarbon separations, include chromatography and centrifugalforce.

Chromatography has many variations and can be performed on a large scalefor chemical separation or on a microscale for analytical purposes.Chromatographic methods generally rely on differences in the affinitiesof the various members of a group of dissolved or gaseous chemicals fora certain adsorbent. Typically, all chromatographic methods have amobile and a stationary phase. The mixture is placed in the mobile phasethat is then passed through the adsorbent-containing stationary phase.The different components of the mixture have different affinities forthe adsorbent in the stationary phase, and these differences inaffinities result in different rates of passage through the stationaryphase, resulting in the separation.

Centrifuging is commonly used for separating solids from liquids (whereone of the materials to be separated can be solidified) and for liquidfrom liquid mixtures. Centrifuging generally utilizes a centrifugedevice that spins its contents either vertically or horizontally toincrease the normal effect of gravity. In a rotating centrifuge, thedenser particles will generally move to the outside of a cylinder, whilethe lighter particles remain near the center of that cylinder.

For many chemical processes, such solid-liquid separation methods oftenplay an important role in the isolation and manufacture of intermediatechemical streams. The separation of aromatics, and in particular, xyleneisomers are quite suitable due to advances in crystallizationtechnology, which permits a chemical plant operator to crystallizediscrete xylene isomers from a mixture of xylene isomers.Crystallization combined with efficient solid-liquid separationtechniques is of interest because of the usefulness of paraxylene in themanufacture of terephthalic acid, an intermediate in the manufacture ofpolyester. Specifically, paraxylene having a purity of at least about 99weight percent, more preferably at least about 99.5 weight percent, morepreferably of at least about 99.7 weight percent, is most suitable forthe manufacture of terephthalic acid by the oxidation of paraxylene.

Current commercial processes for separating xylene isomers include theaforementioned chromatography, and crystallization followed bycentrifugation. Crystallization, rather than distillation, is typicallya more suitable option to separate xylene isomers due to the fact thattheir respective freezing points are far apart, while their boilingpoints are in close proximity. For example, pure paraxylene freezes at56° F., pure metaxylene freezes at −54° F., pure orthoxylene freezes at−13° F., and pure ethylbenzene freezes at −139° F. Equilibrium mixturesof xylene isomers generally contain about 25 weight percent paraxylene,about 25 weight percent orthoxylene, and about 50 weight percentmetaxylene.

Due to the low concentration of paraxylene in these mixed xylene streamsand the disparate freezing points of the xylene isomers, very lowtemperatures are generally required to ensure maximum recovery ofparaxylene from a C₈ fraction by crystallization. However, there is anoperational low temperature limit generally taken as themetaxylene/paraxylene or the orthoxylene/paraxylene binary eutectictemperature that prevents the complete recovery of all the paraxylenefrom a C₈ fraction.

At or below this limit, either metaxylene or orthoxylene willco-crystallize with paraxylene. Furthermore, if the temperature fallsbelow either of the binary eutectic temperatures, then a second solidphase which is lean in paraxylene will crystallize from the mixture. Theformation of a second solid phase is generally viewed as undesirable, socrystallization processes are typically operated at as cold atemperature as possible, but at a temperature warmer than the warmestbinary eutectic temperature. While this constrains the once-throughparaxylene recovery of the process, conventional paraxylene separationprocesses that use crystallization produce a substantially pureparaxylene product.

Although such crystallization processes produce a paraxylene productwith a purity level in excess of 98 percent, the use of centrifuges,centrifuge-like devices, and other solid-liquid separation devices canadd significant costs to the purification process due to their highcapital costs and the high maintenance costs inherent in high speedrotating parts. In addition, such devices are expensive to buy, install,operate, and maintain. They are also a reliability problem since evenwell-maintained centrifuges are apt to shut down unexpectedly. As aresult, prior efforts have focused on developing alternatives tocentrifugation to improve the economics of producing substantially pureparaxylene.

U.S. Pat. Nos. 4,734,102 and 4,735,781, issued to Thijssen et al.disclose solid-liquid separation processes and apparatuses that functionwith minimal moving parts. The process and apparatus of Thijssen '102and '781 utilize a closed column having at least one filter tube havinga filter. A suspension is directed into one end of the column, and awashing liquid into a second end of the column in countercurrent flow tothe suspension, forming a bed in the column. A filtrate stream from thesuspension is removed through the filters of the filter tubes into theinterior of the tubes, and a concentrated suspension is withdrawn fromthe second end of the column. A wash liquid is introduced at the secondend to wash and reslurry the concentrated suspension, When the processis used to separate a suspension derived from a melt crystallizationprocess, the wash liquid comprises molten crystal product from thesuspension.

Although the processes and apparatuses disclosed in Thijssen '102 and'781 avoid centrifuging, these processes have disadvantages that havelimited their broad application.

The process disclosed in the Thijssen patents cannot effectivelyseparate liquids from solids at processing temperatures far below themelting point of slurry crystals derived from a melt crystallizationprocess. This is because the wash liquid utilized during the processfreezes within the column during the washing part of the process. Atincreasingly lower temperatures, the freezing wash liquid fills a largerportion of the void fraction between the solids, thereby requiringhigher and higher pressures to drive the wash liquid into the column.Eventually, a low enough temperature will be reached wherein thefreezing wash liquid essentially plugs the device, causing failure andimminent shutdown of the apparatus and process disclosed in the Thijssenpatents. In the case of the separation of paraxylene from xyleneisomers, the application of this technology would preclude themanufacturer from operating its crystallization process at aggressivelylow crystallization temperatures so as to maximize paraxylene recoveryby challenging the binary eutectic temperatures described above.

Yet another disadvantage is that the use of a molten solids wash liquidin the process disclosed in the Thijssen patents can contaminate thefiltrate with a liquid that may not be easily or inexpensively separatedfrom the filtrate. This can result in a substantial loss of solidproduct to the filtrate.

Consequently, there is still a great need in the industry foralternative processes and apparatuses for separation of solids fromliquids that address and solve the problems noted above.

It has now been found that filter column apparatuses in accordance withthe present invention and comprising a filtration zone and a reslurryzone substantially separated by a barrier wall provides substantialenergy and capital savings benefits over apparatuses that do not featuresuch a barrier wall.

It has also been found that a filter column apparatus comprising afiltration zone and a reslurry zone in substantial cooperation with oneanother provides for substantial energy and capital savings overapparatuses where reslurry operations occur in separate downstreamvessels.

It has also been found that processes for separating at least a portionof one or more substantially solid components from a solid-liquidstream, in a filtration zone, by contacting at least a portion of thesubstantially solid components and/or the solid-liquid stream with animmiscible fluid, such as a gas, produces a relatively dry and pureproduct stream of substantially solid components.

It has also been found that processes for purifying paraxylene from asolid-liquid stream having a wide range of temperatures, in a filtrationzone, by contacting at least a portion of either substantially solidparaxylene or said solid-liquid stream with an immiscible fluid, such asa gas, in lieu of a wash liquid, produces a relatively dry and pureproduct stream comprising substantially solid paraxylene, which can befurther processed with little or no additional refrigeration costs.

SUMMARY OF THE INVENTION

One aspect of this invention is a filter column apparatus comprising afiltration zone and a substantially enclosed reslurry zone. Thefiltration zone and substantially enclosed reslurry zones are separatedby a barrier wall.

Another aspect of this invention is a filter column apparatus comprisinga substantially enclosed filtration zone and a reslurry zone. Thesubstantially enclosed filtration zone and said reslurry zone areseparated by a barrier wall.

Another aspect of this invention is a filter column apparatus comprisinga filtration zone and a reslurry zone. The filtration zone and saidreslurry zone are in substantial cooperation with one another.

Another aspect of this invention is a process for separating at least aportion of one or more substantially solid components from asolid-liquid stream comprising said substantially solid components andone or more substantially liquid components. The process comprisescontacting at least a portion of the solid-liquid stream, and/or atleast a portion of the substantially solid component, with an immisciblefluid, and passing at least a portion of said substantially liquidcomponent and at least a portion of said immiscible fluid through atleast one filter and forming a filtrate. The process further comprisesremoving an enriched product stream comprising the substantially solidcomponents. The process takes place in a filtration zone comprising atleast one filter, an area of higher concentration of substantially solidcomponents, and an area of lower substantially solid components. Thefiltration zone may also comprise at least one filter, a higher pressurezone, and a lower pressure zone.

Another aspect of this invention is a packed bed process for separatingat least a portion of a substantially solid component from asolid-liquid stream comprising said substantially solid component and atleast one substantially liquid component. The process comprises applyingan immiscible fluid for assisting formation of a substantially solidscontaining packed bed, further defining bed void space. The processfurther comprises passing at least a portion of the substantially liquidcomponent through the bed void space of the substantially solidscontaining packed bed, thus leaving an enriched product streamcomprising said at least one substantially solid component.

Another aspect of this invention is a start up process for forming asubstantially solids containing packed bed. The process comprisescontacting a solid-liquid stream comprising at least one substantiallysolid component and at least one substantially liquid component with animmiscible fluid, and directing at least a portion of said at least onesubstantially liquid component through at least one filter to form saidsubstantially solids containing packed bed, wherein said bed furtherdefines a bed void space. The process further comprises passing at leasta portion of said at least one substantially liquid component throughsaid bed void space of substantially solids containing packed bed.

Another aspect of this invention is a process for separating at least aportion of substantially solid paraxylene from a solid-liquid streamcomprising said substantially solid paraxylene and a substantiallyliquid aromatics stream. The process comprises contacting an immisciblefluid with one or both of said solid-liquid stream, or at least aportion of said substantially solid paraxylene. The process furthercomprises passing at least a portion of said substantially liquidaromatics stream, and at least a portion of said immiscible fluidthrough at least one filter and forming a filtrate comprising saidsubstantially liquid aromatics stream and said immiscible fluid, thusleaving an enriched product stream comprising said substantially solidparaxylene. This enriched product stream is reslurried with a flush feedand further processed to produce a purified, paraxylene product. Theprocess occurs in a filtration zone comprising at least one filter, anarea of higher concentration of substantially solid paraxylene, and anarea of lower concentration of substantially solid paraxylene. Thefiltration zone may also comprise at least one filter, a higher pressurezone, and a lower pressure zone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a cross-sectional view of a filter column apparatus witha substantially enclosed reslurry zone.

FIG. 2 depicts a cross-sectional view of a filter column apparatus witha substantially enclosed filtration zone.

FIG. 3 depicts a cross-sectional view of a filter column in substantialcooperation with a chute.

FIGS. 4 a-d depict a cross-sectional view of a start-up procedure for afilter column and filtration process in accordance with the subjectinvention.

DETAILED DESCRIPTION OF THE INVENTION

The application of filter columns in the present invention, as describedin more detail below, can be used in processes to separate at least onesubstantially solid component from a solid-liquid stream comprising thesubstantially solid component and at least one substantially liquidcomponent. As used herein, the recitations of “substantially solidcomponent” and “substantially liquid component” shall refer to at leastone substantially solid component or at least one substantially liquidcomponent, or similarly, one or more substantially solid components, orone or more substantially liquid components. Preferably, this inventionprovides for the application of filter columns at the intermediate stepsof such solid-liquid separation processes to assist in the efficient andeffective recovery of purified paraxylene.

The solid-liquid stream used in this invention is generally a mixture ofa substantially solid component and a substantially liquid component.Suitable solid-liquid streams comprise between from about 0.5 weightpercent to about 65 weight percent of a substantially solid component,from about 5 weight percent to about 60 weight percent of asubstantially solid component, and more preferably between about 10weight percent to about 55 weight percent of a substantially solidcomponent for best results. For aromatic crystallization processes, sucha substantially solid component often comprises substantially solidparaxylene. Optionally, this substantially solid component may comprisesmall amounts of orthoxylene, metaxylene, ethylbenzene, and otherhydrocarbons such as paraffins, naphthenes, benzene, and toluene. Such asolid-liquid stream may also comprise between about 35 weight percent toabout 95 weight percent of a substantially liquid component, betweenabout 45 weight percent to about 90 weight percent of a substantiallyliquid component, and more preferably between about 40 weight percent toabout 85 weight percent of a substantially liquid component. Foraromatics crystallization processes, the substantially liquid componentoften comprises paraxylene, metaxylene, orthoxylene, ethylbenzene, andother hydrocarbons, such as paraffins, naphthenes, benzene, and toluene.

Preferably, solid-liquid streams utilized in this invention arise from,or are the direct or indirect product or byproduct of, processes whichproduce, contain, or recover paraxylene. Streams from which paraxyleneis recovered are often derived from catalytic reforming processes foundin many petroleum refineries. Other streams containing paraxyleneinclude pyrolysis gasoline, conventional toluene disproportionationproducts, and conventional transalkylation products.

In many of the above-mentioned streams, the xylene isomers are generallynear their equilibrium distribution, which is about 25% paraxylene,about 50% metaxylene, and about 25% orthoxylene. The low equilibriumconcentration of paraxylene is further diluted by the presence ofethylbenzene, such that the C₈ fraction derived by distillation fromreformate typically comprises from about 10 to about 20 weight percentethylbenzene, and more typically from about 15 to about 18 weightpercent ethylbenzene. Furthermore, the presence of other compounds suchas benzene, toluene, and other hydrocarbons such as paraffins andnaphthenes also lower the paraxylene concentration. The C₈ fraction ofpyrolysis gasoline typically comprises as much as about 30 to about 60weight percent ethylbenzene, whereas the C₈ fraction of conventionaltoluene disproportionation typically comprises only about 2 to about 7weight percent ethylbenzene. Dilution by ethylbenzene and othercompounds and the equilibrium distribution of the xylene isomers reducesthe paraxylene content of these streams to as low as about 10 to about25 weight percent paraxylene, with reformate mixed xylene streamstypically comprising about 15 to about 20 weight percent paraxylene.These streams may be preprocessed to selectively remove metaxylene ororthoxylene, which would increase the paraxylene concentration. Thus,streams with relatively lower paraxylene concentrations as describedabove generally comprise less than about 50 weight percent paraxylene,typically less than about 35 weight percent paraxylene, and moretypically less than about 25 weight percent paraxylene.

Streams with relatively higher paraxylene concentrations (relative tothe aforementioned streams) arise from sources including streamsproduced by selective toluene disproportionation (STDP), selectivealkylation, selective transalkylation, as described in U.S. Pat. No.4,097,543 and U.S. Pat. No. 4,117,026, and in W. W. Kaeding, et al., J.Catal., 67, 159 (1981), or intra-stage products of paraxylene recoveryprocesses as found in the second or subsequent stages of multi-stagecrystallization processes. Other streams with relatively higherparaxylene concentration also include the paraxylene-enriched streamproduced in the selective adsorption zone of a hybridadsorption/crystallization paraxylene process, such as that described inU.S. Pat. No. 5,329,060.

Paraxylene recovery processes are often based on crystallization orselective adsorption technology. Briefly, paraxylene crystallizationprocesses generally comprise an isomerization section, a fractionationsection, and a crystallization section. Some crystallization processesmay also comprise slurry sections. Such crystallization processes mayinclude one or more crystallization stages which generally comprisejacketed crystallizers, which are typically scraped wall vessels withrefrigerated jackets through which a vaporizing refrigerant passes.Crystallization processes tend to be most suitable for use with thepresent invention because they separate and purify through theproduction of solids.

An example of a molecular sieve adsorption process would be “Parex.”“Parex” is a commonly applied molecular sieve adsorption process, asdescribed in D. P. Thornton, Hydrocarbon Proc. 49 (1970) at pp. 151-155,which is incorporated herein by reference. This process is based on theprinciple of continuous selective adsorption in the liquid phaseemploying fixed beds of solid adsorbent. The adsorbent is made from azeolite, and the separation technique is based on small differences inaffinity to the adsorbent. Paraxylene has the strongest affinity to theadsorbent and is thus preferentially adsorbed.

In so far that such processes generate solid-liquid streams comprisingsubstantially solid paraxylene, this invention provides for theapplication of filter columns at the intervening steps of such processesto assist in the efficient and effective recovery of a purifiedparaxylene product.

FIG. 1 depicts a cross-sectional view of a filter column apparatus witha substantially enclosed reslurry zone, RZ1. In FIG. 1, filter column101 comprises a substantially hollow cavity 102 having a substantiallyclosed end 103 and a substantially open end 104. The filter column 101can be substantially tubular or substantially cylindrical in shape.Within the substantially hollow cavity 102, at least one filter tube 105extends in an axial direction, with at least one filter tube 105 havinga top portion 106 and a bottom portion 107. As used herein, therecitations of “filter tube” shall refer to at least one filter tube.The top portion 106 of filter tube 105 is closed.

The filter tube 105 is generally situated in substantial proximity to aninner wall 108 inside of filter column 101. The inner wall 108 is alsogenerally situated in substantial proximity to a barrier wall 110, whichis also located inside filter column 101. Preferably, filter tube 105 issituated substantially between said barrier wall 110 and said inner wall108. The bottom portion 107 of filter tube 105 extends through thesubstantially closed end 103 of the substantially hollow cavity 102,with the bottom portion 107 of the filter tube 105 having an opening 107a at a terminal end. Such an opening may provide for the passage ofsubstantially liquid component, or an immiscible fluid (describedhereafter), either individually or in combinations thereof. The filtertube 105 comprises at least one filter 109, attached, integrated, orotherwise affixed to the filter tube 105, forming a connection for flowof substantially liquid component or an immiscible fluid, eitherindividually or in combinations thereof, between the interior of thesubstantially hollow cavity 102 and the interior of filter tube 105.Optionally, the filter 109 may be attached, integrated, or otherwiseaffixed to barrier wall 110 and/or inner wall 108. As used herein, therecitations of “filter” shall refer to at least one filter.

In FIG. 1, the area surrounding or outside of filter 109, or optionallythe area surrounding or outside of filter tube 105 describes an area ofhigher concentration of the substantially solid component (higherconcentration zone). Alternatively, this area also describes an area ofhigher pressure (higher pressure zone). The area within or inside offilter 109, or optionally the area within or inside of filter tube 105describes an area of lower concentration of the substantially solidcomponent (lower concentration zone). Alternatively, this area alsodescribes an area of lower pressure (lower pressure zone). These areasgenerally at, near, or in substantial proximity to filter 109, oroptionally at, near, or in substantial proximity to filter tube 105describe a filtration zone. The filtration zone of this embodiment issubsequently referred to herein as FZ1.

The area of higher concentration of the substantially solid componenthas a greater weight percent of the substantially solid component thanthe area of lower concentration of the substantially solid component.This concentration differential can be measured by any means suitable todemonstrate a concentration gradient across filter 109 in the filtrationzone FZ1. For example, the concentration of the substantially solidcomponent in the area of higher concentration of the substantially solidcomponent can be determined by measuring the weight percent of thesubstantially solid component in the solid-liquid stream directed intothe area of higher concentration of the substantially solid component.Likewise, the concentration of the substantially solid component in thearea of lower concentration of the substantially solid component can bedetermined by measuring the weight percent of the substantially solidcomponent in a filtrate withdrawn from the filter column at 114.

Alternatively, as stated, the filtration zone FZ1 can be defined by anarea of higher pressure (a higher pressure zone) and an area of lowerpressure (a lower pressure zone), wherein said areas are separated byfilter 109. The area of higher pressure is at a higher pressure than thearea of lower pressure, and this pressure differential can be measuredby any means suitable to demonstrate a pressure gradient across filter109 in the filtration zone FZ1. For example, the pressure level in thearea of higher pressure can be determined by measuring the pressure ofthe solid-liquid stream directed into the area of higher pressure, andthe pressure level of the area of lower pressure can be determined bymeasuring the pressure of the substantially liquid component comprisingfiltrate withdrawn from the filter column 101. Additionally, fluids flowfrom the area of high pressure to the area of low pressure. Thus, theflow of the substantially liquid component portion of the solid-liquidstream through filter 109 indicates a pressure differential between thearea of higher pressure and the area of lower pressure across the filter109.

Filter column 101 further comprises a substantially curved section ofinner wall 108 through which the open end 104 of the substantiallyhollow cavity 102 is exposed. Such substantially curved section isdepicted as 108 a. At or near the closed end 103 of the substantiallyhollow cavity 102, there is preferably at least one solid-liquid streaminlet 111 to direct a solid-liquid stream into the substantially hollowcavity 102. Filter column 101 further may comprise at least oneimmiscible fluid inlet line 112 to direct an immiscible fluid into thesubstantially hollow cavity 102.

Such an immiscible fluid is used to displace the substantially liquidcomponent from the solid-liquid stream, or to form a blanket within atleast a portion of substantially hollow cavity 102. For FIGS. 1-3,inclusively, the immiscible fluid is preferably a gas. Non-limitingexamples of such a gas include nitrogen, carbon dioxide, compressed air,hydrogen, helium, xenon, argon, neon, methane, ethane, natural gas orsteam. Optionally, the immiscible fluid may also be a liquid,substantially insoluble in the substantially solid component of saidsolid-liquid stream. If a liquid, the immiscible fluid is alsosubstantially insoluble in the substantially liquid component of thesolid-liquid stream, allowing for relatively easy subsequent separationof the immiscible fluid from the filtrate. Optionally, the immisciblefluid may also be a supercritical fluid.

For FIGS. 1-3, inclusively, the immiscible fluid can be provided at anytemperature suitable for separating the substantially liquid componentfrom the substantially solids component from a particular solid-liquidstream. Preferably, the immiscible fluid is at a temperature lower thanthe temperature of the solid-liquid stream. The lower temperature of theimmiscible fluid can be utilized to further crystallize at least aportion of the substantially liquid component or maintain thesubstantially solid component in the solid-liquid stream, thus providingfor improved solids recovery. Alternatively, the immiscible fluid can beprovided at a higher temperature than the temperature of thesolid-liquid stream. The higher temperature of the immiscible fluid canbe utilized to facilitate the removal of residual substantially liquidcomponent from the substantially solid component, producing a remainingenriched product stream comprising the substantially solid component.Yet alternatively, the temperature of the immiscible fluid is about thesame as the temperature of the solid-liquid stream in order to practicethe process under substantially isothermal conditions. Optionally, ifthe immiscible fluid is a gas and the amount of gas is small compared tothe amount of the substantially solid component in the solid-liquidstream, the temperature of the immiscible fluid is relativelyirrelevant, as the amount of energy introduced to the device by the gasis insignificant and the unit operates at substantially isothermalconditions over a wide range of gas temperatures.

Filter column 101 may further comprise at least one line to direct aflush feed 113 into said substantially hollow cavity 102 to clear anyobstructions such as packed, substantially solid component lodged in thesubstantially hollow cavity 102. Such a flush feed can be any gas orliquid capable of clearing the filter column of obstructions. Typically,the flush feed may comprise an inert gas, including, but not limited to,nitrogen or carbon dioxide. Alternatively, the flush feed comprises airor hydrogen. Yet alternatively, the flush feed may comprise at least aportion of the substantially liquid component comprising a filtrateproduced during the process either according to this invention or from aconventional solid-separation device, such as a centrifuge. In the caseof separating paraxylene crystals from a solid-liquid of mixed xylenes,the flush feed preferably comprises C₈ aromatics.

Within the filter column 101 lays reslurry zone, RZ1. An enrichedproduct stream comprising the substantially solid component is separatedin and directed from the filtration zone, FZ1, into the reslurry zone,RZ1. At this point, the enriched product stream comprising thesubstantially solid component is in the form of a relatively dry cakewhen utilizing a gaseous immiscible fluid. The enriched product streamcomprising the substantially solid component is reslurried with flushfeed 113. The slurry mixture of flush feed 113 and the enriched productstream comprising the substantially solid component in reslurry zone RZ1may optionally be agitated. The reslurry zone RZ1 preferably has aliquid level, as depicted in FIG. 1, to prevent and seal against theescape of immiscible fluid out of the reslurry zone along with effluentstream 114, which comprises a mixture of flush feed 113 and the enrichedproduct stream comprising the substantially solid component. Thereslurry zone RZ1 may further comprise a straining means to assist withthe reslurry of the enriched product stream comprising the substantiallysolid component with flush feed 113, Optionally, a heat source, in lieuof the flush feed 113, may be incorporated into the reslurry zone tomelt at least a portion of the enriched product stream comprising thesubstantially solid component.

The reslurry zone RZ1 is operated at a sufficiently high temperature sothat the resulting effluent stream 114 from the reslurry zone can besent to one or more solid-liquid separation devices (not shown) that arecapable of producing more enriched substantially solid component, whichis further processed using conventional techniques to eventually recovera purified, paraxylene product. Such a purified paraxylene productcomprises at least about 99 weight percent paraxylene, more preferablyat least about 99.5 weight percent paraxylene, and yet more preferablyat least about 99.7 weight percent paraxylene. Such solid-liquidseparation devices are well-known in the art, and include, but are notlimited to, solid bowl, screen bowl or pusher type centrifuges andcombinations thereof, wash columns, or rotary filters. Alternatively,the effluent stream 114 could be sent to another filter column.

The reslurry zone RZ1 and the filtration zone FZ1 are separated by abarrier wall 110. In this embodiment, the barrier wall 110 substantiallyencloses the reslurry zone RZ1 from the filtration zone FZ1. The barrierwall also has thermal insulation properties which keeps the filtrationzone FZ1 relatively cool and the reslurry zone RZ1 relatively warm. Inaddition, the filtration zone FZ1 is annularly disposed around saidsubstantially enclosed reslurry zone RZ1, as separated by said barrierwall. Both the reslurry zone RZ1 and the filtration zones FZ1 areconfigured within filter column 101 with each zone defining its ownsubstantially central axis within each respective zone. In addition, thesubstantially central axis of the reslurry zone RZ1 and that of thefiltration zone FZ1 are in substantial proximity to each other.

FIG. 2 shows a cross-sectional view of a filter column apparatus with asubstantially enclosed filtration zone. Referring to FIG. 2, a filtercolumn 201 comprises a substantially hollow cavity 202 having a closedend 203 and an open end 204. The filter column 201 can be substantiallytubular or cylindrical in shape. Within the substantially hollow cavity202, at least one filter tube 205 extends in an axial direction, withthe at least one filter tube 205 having a top portion 206 and a bottomportion 207. The top portion 206 of filter tube 205 is closed.

The filter tube 205 is generally situated in substantial proximity to abarrier wall 208 inside of said filter column 201. The bottom portion207 of filter tube 205 extends through the closed end 203 of thesubstantially hollow cylinder 202, with the bottom portion 207 having anopening 207 a at a terminal end. The filter tube 205 comprises at leastone filter 209, attached, integrated, or otherwise affixed to filtertube 205, forming a connection for flow of substantially liquidcomponent or an immiscible fluid, either individually or in combinationsthereof, between the interior of the substantially hollow cavity 202 andthe interior of filter tube 205. Optionally, filter 209 may be attached,integrated, or otherwise affixed to barrier wall 208.

In FIG. 2, the area surrounding or outside of filter 209, or optionallythe area surrounding or outside of filter tube 205 describes an area ofhigher concentration of the substantially solid component (higherconcentration zone). Alternatively, this area also describes an area ofhigher pressure (higher pressure zone). The area within or inside offilter 209, or optionally the area within or inside of filter tube 205describes an area of lower concentration of the substantially solidcomponent (lower concentration zone). Alternatively, this area alsodescribes an area of lower pressure (lower pressure zone). These areasgenerally at, near, or in substantial proximity to filter 209, oroptionally at, near, or in substantial proximity to filter tube 205describe a filtration zone. The filtration zone of this embodiment issubsequently referred to herein as FZ2.

The area of higher concentration of the substantially solid componenthas a greater weight percent of the substantially solid component thanthe area of lower concentration of the substantially solid component.This concentration differential can be measured by any means suitable todemonstrate a concentration gradient across filter 209 in the filtrationzone FZ2. For example, the concentration of the substantially solidcomponent in the area of higher concentration of the substantially solidcomponent can be determined by measuring the weight percent of thesubstantially solid component in the solid-liquid stream directed intothe area of higher concentration of the substantially solid component.Likewise, the concentration of the substantially solid component in thearea of lower concentration of the substantially solid component can bedetermined by measuring the weight percent of the substantially solidcomponent in a filtrate withdrawn from the filter column at 214.

Alternatively, as stated, the filtration zone FZ2 can be defined by anarea of higher pressure (a higher pressure zone) and an area of lowerpressure (a lower pressure zone), wherein said areas are separated byfilter 209. The area of higher pressure is at a higher pressure than thearea of lower pressure, and this pressure differential can be measuredby any means suitable to demonstrate a pressure gradient across filter209 in the filtration zone FZ2. For example, the pressure level in thearea of higher pressure can be determined by measuring the pressure ofthe solid-liquid stream directed into the area of higher pressure, andthe pressure level of the area of lower pressure can be determined bymeasuring the pressure of the substantially liquid component comprisingfiltrate withdrawn from the filter column 201. Additionally, fluids flowfrom the area of high pressure to the area of low pressure. Thus, theflow of the substantially liquid component portion of the solid-liquidstream through filter 209 indicates a pressure differential between thearea of higher pressure and the area of lower pressure across the filter209.

Filter column 201 also contains a deflector 210 inside said filtercolumn 201 through which the open end 204 of the substantially hollowcavity 202 is exposed. The deflector 210 is used to deflect an enrichedproduct stream comprising the substantially solid component from thefilter tube 205 towards a reslurry zone RZ2. The reslurry zone of FIG. 2functions in the same manner as described for FIG. 1.

At or near the closed end 203 of the substantially hollow cavity 202, itis preferred that there is at least one solid-liquid feed inlet 211 todirect a solid-liquid stream into the substantially hollow cavity 202.Filter column 201 further may comprise at least one immiscible fluidinlet line 212 to direct an immiscible fluid preferably into thesubstantially hollow cavity 202. Such an immiscible fluid is used todisplace the substantially liquid component from the solid-liquidstream, or to form a blanket within at least a portion of thesubstantially hollow cavity 202. Filter column 201 may further compriseat least one line to direct a flush feed 213 into said substantiallyhollow cavity 202 to clear any obstructions such as packed,substantially solid component lodged in the substantially hollow cavity202. The flush feed functions in the same manner as described for FIG.1.

The reslurry zone RZ2 and the filtration zone FZ2 are separated bybarrier wall 208. The barrier wall 208 substantially encloses thereslurry zone RZ2 from the filtration zone FZ2. The barrier wall alsohas thermal insulation properties which keeps the filtration zone FZ2relatively cool and the reslurry zone RZ2 relatively warm. In addition,the reslurry zone RZ2 is annularly disposed around said substantiallyenclosed filtration zone FZ2, as separated by said barrier wall. Boththe reslurry zone RZ2 and the filtration zone FZ2 are configured withinfilter column 201, with each zone defining its own substantially centralaxis within each respective zone. In addition, the substantially centralaxis of both the reslurry zone RZ2 and filtration zone FZ2 are insubstantial proximity to each other.

Within the filter column 201 lays reslurry zone RZ2, wherein an enrichedproduct stream comprising the substantially solid component is directedfrom the filtration zone, FZ2. At this point, the enriched productstream comprising the substantially solid component is in the form of arelatively dry cake when utilizing a gaseous immiscible fluid. Theenriched product stream comprising the substantially solid component isreslurried with flush feed 213. The slurry mixture of flush feed 213 andthe enriched product stream comprising the substantially solid componentin reslurry zone RZ2 may optionally be agitated. The reslurry zone RZ2preferably has a liquid level, as depicted in FIG. 2, to prevent andseal against the escape of immiscible fluid out of the reslurry zonealong with effluent stream 214, which comprises a mixture of flush feed213 and the enriched product stream comprising the substantially solidcomponent. The reslurry zone RZ2 may further comprise a straining meansto assist with the reslurry of the enriched product stream comprisingthe substantially solid component with flush feed 213. Optionally, aheat source, in lieu of the flush feed 213, may be incorporated into thereslurry zone to melt at least a portion of the enriched product streamcomprising the substantially solid component.

The reslurry zone RZ2 is preferably operated at a sufficiently hightemperature so that the resulting effluent stream 214 from the reslurryzone can be sent to one or more solid-liquid separation devices (notshown) that are capable of producing more enriched substantially solidcomponents, which are further processed using conventional techniques toeventually recover a purified, paraxylene product. Such a purifiedparaxylene product comprises at least about 99 weight percentparaxylene, more preferably 99.5 weight percent paraxylene, and yet morepreferably at least about 99.7 weight percent paraxylene. Suchsolid-liquid separation devices are well-known in the art, and include,but are not limited to, solid bowl, screen bowl or pusher typecentrifuges and combinations thereof, wash columns, or rotary filters.Alternatively, the effluent stream 214 could be sent to another filtercolumn.

FIG. 3 depicts a cross-sectional view of a filter column in substantialcooperation with a chute 310. “Substantial cooperation” as used hereinmeans more than one vessel attached, integrated, affixed, or otherwiseassociated with one another. Referring to FIG. 3, a filter column 301comprises a substantially hollow cavity 302 having a closed end 303 andan open end 304. The filter column 301 can be substantially tubular orcylindrical in shape. Within the substantially hollow cavity 302, atleast one filter tube 305 extends in an axial direction, with at leastone filter tube 305 having a top portion 306 and a bottom portion 307.The top portion 306 of filter tube 305 is closed. The filter tube 305 isgenerally situated in substantial proximity to an inner wall 308 of saidfilter column 301. The bottom portion 307 of filter tube 305 extendsthrough the closed end 303 of the substantially hollow cylinder 302, thebottom portion 307 having an opening 307 a at a terminal end. Filtertube 305 comprises at least one filter 309, attached, integrated, orotherwise affixed to at least one filter tube 305, forming a connectionfor flow of substantially liquid component or an immiscible fluid,either individually or in combinations thereof, between the interior ofthe substantially hollow cavity 302 and the interior of filter tube 305.Optionally, the filter 309 may be attached, integrated, or otherwiseaffixed to inner wall 308.

In FIG. 3, the area surrounding or outside of filter 309, or optionallythe area surrounding or outside of filter tube 305 describes an area ofhigher concentration of the substantially solid component (higherconcentration zone). Alternatively, this area also describes an area ofhigher pressure (higher pressure zone). The area within or inside offilter 309, or optionally the area within or inside of filter tube 305describes an area of lower concentration of substantially solidcomponent (lower concentration zone). Alternatively, this area alsodescribes an area of lower pressure (lower pressure zone). These areasgenerally at, near, or in substantial proximity to filter 309, oroptionally at, near, or in substantial proximity to filter tube 305describe a filtration zone. The filtration zone of this embodiment issubsequently referred to herein as FZ3. The filtration zone FZ3 isconfigured within filter column 301 as being defined around asubstantially central axis.

The area of higher concentration of the substantially solid componenthas a greater weight percent of the substantially solid component thanthe area of lower concentration of the substantially solid component.This concentration differential can be measured by any means suitable todemonstrate a concentration gradient across filter 309 in the filtrationzone FZ3. For example, the concentration of the substantially solidcomponent in the area of higher concentration of the substantially solidcomponent can be determined by measuring the weight percent of thesubstantially solid component in the solid-liquid stream directed intothe area of higher concentration of the substantially solid component.Likewise, the concentration of the substantially solid component in thearea of lower concentration of the substantially solid component can bedetermined by measuring the weight percent of the substantially solidcomponent in a filtrate withdrawn from the filter column at 314.

Alternatively, as stated, the filtration zone FZ3 can be defined by anarea of higher pressure (a higher pressure zone) and an area of lowerpressure (a lower pressure zone), wherein said areas are separated byfilter 309. The area of higher pressure is at a higher pressure than thearea of lower pressure, and this pressure differential can be measuredby any means suitable to demonstrate a pressure gradient across filter309 in the filtration zone FZ3. For example, the pressure level in thearea of higher pressure can be determined by measuring the pressure ofthe solid-liquid stream directed into the area of higher pressure, andthe pressure level of the area of lower pressure can be determined bymeasuring the pressure of the substantially liquid component comprisingfiltrate withdrawn from the filter column 301. Additionally, fluids flowfrom the area of high pressure to the area of low pressure. Thus, theflow of the substantially liquid component portion of the solid-liquidstream through filter 309 indicates a pressure differential between thearea of higher pressure and the area of lower pressure across the filter309.

At or near the closed end 303 of the substantially hollow cavity 302, itis preferred that there is at least one solid-liquid stream inlet 311 todirect a solid-liquid stream into the substantially hollow cavity 302.Filter column 301 further may comprise at least one immiscible fluidinlet line 312 to direct an immiscible fluid preferably into thesubstantially hollow cavity 302. Such an immiscible fluid is used todisplace the substantially liquid component from the solid-liquidstream, or to form a blanket within at least a portion of substantiallyhollow cavity 302. Filter column 301 may further comprise at least oneline to direct a flush feed 313 into said substantially hollow cavity302 to clear any obstructions such as packed, substantially solidcomponent lodged in the substantially hollow cavity 302. The flush feedfunctions in the same manner as described for FIG. 1.

Filter column 301 is in substantial cooperation with chute 310. Chute310 contains therein a reslurry zone RZ3. Chute 310 may further comprisea straining means to assist with the reslurry of the substantially solidcomponent with the flush feed 313.

An enriched product stream comprising the substantially solid componentis separated in and directed from the filtration zone, FZ3, into thereslurry zone RZ3. At this point, the enriched product stream comprisingthe substantially solid component is in the form of a relatively drycake when utilizing a gaseous immiscible fluid. The enriched productstream comprising the substantially solid component is reslurried withflush feed 313. The slurry mix of flush feed 313 and the enrichedproduct stream comprising the substantially solid component in reslurryzone RZ3 may optionally be agitated. The reslurry zone RZ3 preferablyhas a liquid level, as depicted in FIG. 3, to prevent and seal againstthe escape of immiscible fluid out of the reslurry zone along witheffluent stream 314, which comprises a mixture of flush feed 313 and theenriched product stream comprising the substantially solid component.Optionally, a heat source, in lieu of the flush feed 313, may beincorporated into the reslurry zone to melt at least a portion of theenriched product stream comprising the substantially solid component.

The reslurry zone RZ3 is operated at a sufficiently high temperature sothat the resulting effluent stream 314 from the reslurry zone can besent to one or more solid-liquid separation devices (not shown) that arecapable of producing more enriched substantially solid component, whichis further processed using conventional techniques to eventually recovera purified, paraxylene product. Such a purified paraxylene productcomprises at least about 99 weight percent paraxylene, more preferablyat least about 99.5 weight percent paraxylene, and yet more preferablyat least about 99.7 weight percent paraxylene.

Such solid-liquid separation devices are well-known in the art, andinclude, but are not limited to, solid bowl, screen bowl or pusher typecentrifuges and combinations thereof, wash columns, or rotary filters.Alternatively, the effluent stream 314 could be sent to another filtercolumn.

These aforementioned apparatus embodiments allow for the efficientprocessing of any of the previously described solid-liquid streams.Thus, this invention also provides for the process of separating atleast a portion of the substantially solid component from a solid-liquidstream comprising the substantially solid component and at least onesubstantially liquid component, which is described in more detail below.

The solid-liquid stream can be conveyed into any of the filter columnapparatuses previously described at a pressure sufficient to separate atleast a portion of the substantially solid component from thesubstantially liquid component. During this separation, at least aportion of the solid-liquid stream and/or at least a portion of thesubstantially solid component is contacted with an immiscible fluid.Preferably, said contacting of said solid-liquid stream and immisciblefluid occurs substantially in an area of higher concentration of saidsubstantially solid component (higher concentration zone), oralternatively, in an area of higher pressure (higher pressure zone). Inaddition, the contacting of said solid-liquid stream and immisciblefluid occur in a substantially countercurrent flow. The immiscible fluidis used to separate at least a portion of the substantially liquidcomponent from the substantially solid component through a filtercommunicating with the filter tubes previously described. At least aportion of the immiscible fluid may blanket at least a portion of thesubstantially hollow cavity, filtration zone, or reslurry zone, eitherindividually, or in combinations thereof.

A substantial portion of the substantially liquid component and at leasta portion of the immiscible fluid are removed through the filter as afiltrate, thus leaving a remaining enriched product stream comprisingthe substantially solid component. Preferably after this separation, orpossibly concurrently with this separation, at least a portion of thisenriched product stream comprising the substantially solid component isdirected out of the filtration zone and into the reslurry zone. In thereslurry zone, at least a portion of the enriched product streamcomprising the substantially solid component is reslurried with a flushfeed, and subsequently processed and recovered as a purified product.Preferably, the purified product comprises paraxylene, preferably atleast about 99 weight percent paraxylene, more preferably at least about99.5 weight percent paraxylene, and yet more preferably at least about99.7 weight percent paraxylene.

The immiscible fluid utilized in of any of the embodiments describedherein is conveyed into any of the filter column apparatuses at anopposing pressure sufficient to facilitate the separation of at least aportion of the substantially solid component from the substantiallyliquid component, and for at least a portion of the immiscible fluid topass through the filter to the interior of the filter tube.

Within the filter column, the highest imparted pressure is generally atthe solid-liquid stream inlet. The lowest imparted pressure is generallyat the filter of the filter column at the interior of the filter tube.The pressure at the immiscible fluid inlet is at an intermediate level.Since fluids flow in the direction of high pressure to low pressure,this ensures that the solid-liquid stream in the filter column movestowards the filter and at least a portion of the immiscible fluid.

Generally, when solid components are suspended in liquid, they move inthe same direction as the nearby liquid. For embodiments of thisinvention, at least a portion of the liquid passes through the filter,resulting in at least a portion of the substantially solid componentmoving along with the substantially liquid component and depositing.This deposition forms a dense phase of substantially solid components.This dense phase may also comprise a substantially solids containingpacked bed, further defined by interstitial bed void space. Such asubstantially solids containing packed bed is located at, around, or insubstantial proximity to, and is in substantial cooperation with, thefilter. This packed bed may extend below or above the filter.

For the purposes of the present invention, the dense phase can describean area of substantially solid component concentration within thesubstantially hollow cavity (or higher pressure zone or higherconcentration zone) having a greater concentration of the substantiallysolid component than the solid-liquid stream. The dense phase may alsodescribe a substantially solids containing packed bed wherein is thesubstantially solid component is of such concentration that thesubstantially solid component moves essentially as a solid body withinthe filter column.

When the substantially solid component is deposited as a substantiallysolids containing packed bed, the substantially solid componentgenerally moves in the same direction as the substantially solidscontaining packed bed, as opposed to the direction of immiscible fluidflow towards the filter. However, some substantially solid component maymove and be directed out from the substantially solids containing packedbed as the exiting substantially liquid component passes through theinterstitial bed void space and through the openings in the filter.Nevertheless, the substantially solids containing packed bed movesessentially as a solid body and in a substantially constant direction,although its position in the filter column may remain substantiallyconstant at a steady state.

The direction that the substantially solids containing packed bed moves,or whether the bed moves at all, is generally determined by thesummation of all forces that act on the substantially solids containingpacked bed. One force that is imparted on the substantially solidscontaining packed bed is from the substantially liquid component in thesolid-liquid stream that flows through the packed bed on the way to thefilter. An opposing force is imparted on the substantially solidscontaining packed bed from immiscible fluid blanketing the packed bedand/or flowing to the filter from the opposite end of the filter column.For purposes of the present invention, the immiscible fluid provideshydraulic force if the immiscible fluid is a liquid or pneumatic forceif the immiscible fluid is a gas. Therefore, the substantially solidscontaining packed bed can be pushed by forces from both ends. Thesubstantially solids containing packed bed will move in the desireddirection if the force imparted by the substantially liquid component inthe solid-liquid stream is equal to or larger than the sum of all theopposing forces. In addition, the opposing forces may also include thefrictional forces imparted on the substantially solids containing packedbed that act to impede movement of the substantially solids containingpacked bed and the force of gravity.

Referring again to the figures, these process steps are now described inmore detail. The solid-liquid stream is conveyed near the substantiallyclosed end 103, 203, or 303 of the substantially hollow cavity 102, 202,or 302 of the filter column 101, 201, or 301 via solid-liquid streaminlets 111, 211, or 311. The solid-liquid stream flows through thesubstantially hollow cavity 102, 202, or 302 towards the substantiallyopen end 104, 204, or 304 of the substantially hollow cavity 102, 202,or 302. The immiscible fluid is directed into the substantially hollowcavity 102, 202, or 302 via immiscible fluid inlets 112, 212, or 312.The immiscible fluid flows in a substantially countercurrent manner tothe flow of the solid-liquid stream in the substantially hollow cavity102, 202, or 302, or can blanket the packed bed with little or nocountercurrent flow where the packed bed is sufficiently high above thefilter. To the extent that the solid-liquid stream flows along thefilter 109, 209, or 309, a substantial portion of the substantiallyliquid component passes through the filter 109, 209, or 309 as afiltrate and into the interior of the filter tube 105, 205, or 305.Optionally, a portion of this substantially liquid component may berecycled back to the solid-liquid stream. This filtrate exits the filtercolumn 101, 201, or 301, via the bottom portion 107, 207, or 307 of atleast one filter tube 105, 205, or 305. Substantially in conjunctionwith the substantially liquid component passage, at least a portion ofthe immiscible fluid passes through filter 109, 209, or 309 into theinterior of filter tubes 105, 205, or 305 and exits the filter column101, 201, or 301 via the bottom portion 107, 207, or 307 of filter tube105, 205, or 305. Alternatively, at least a portion of the immisciblefluid may blanket the substantially solids containing packed bed withoutpassing through the filter.

The filtrate exiting the filter column 101, 201, or 301 primarilycomprises the substantially liquid component, but may contain smallamounts of the substantially solid component from the solid-liquidstream. The amount of the substantially solid component present in thefiltrate may be affected by such factors including, but not limited to,the type of the filter employed in the filter column, the size of theopenings in the filter, and the type of solid-liquid stream injectedinto the filter column. However, it is preferred that the filtratecomprise no more than about 20 weight percent solids, more preferably nomore than about 10 weight percent solids, even more preferably no morethan about 5 weight percent solids, and most preferably no more thanabout 1 weight percent solids for best results. The balance of thefiltrate is the substantially liquid component. In the case ofseparating crystallized paraxylene from a solid-liquid stream, thefiltrate may comprise orthoxylene, metaxylene, ethylbenzene, paraxylene,and other hydrocarbons such as paraffins, naphthenes, benzene, andtoluene.

As the substantially liquid component passes through the filter 109,209, or 309 as a filtrate, a dense phase of substantially solidcomponents forms within the substantially hollow cavity 102, 202, or302. In the case of separating crystallized paraxylene from asolid-liquid stream, the substantially solid component comprisesparaxylene, and optionally comprises orthoxylene, metaxylene,ethylbenzene, paraffins, naphthenes, benzene, and toluene. Preferably,the dense phase comprises a substantially solids containing packed bedwithin the substantially hollow cavity 102, 202, or 302 of the filtercolumn 101, 201, or 301 at, near, or in substantial proximity to filtertube 105, 205, or 305. During this formation, a portion of thesubstantially liquid component and at least a portion of the immisciblefluid is removed through the filter, thus leaving a remaining enrichedproduct stream comprising the substantially solid component.Alternatively, at least a portion of the immiscible fluid may blanketthe substantially solids containing packed without passing through thefilter. Preferably after this separation, or possibly concurrently withthis separation, this enriched product stream comprising thesubstantially solid component is directed out of the filtration zones,FZ1, FZ2, or FZ3, and into the reslurry zones RZ1, RZ2, or RZ3 per theembodiments described. In FIG. 1, the enriched product stream comprisingthe substantially solid component is directed toward reslurry zone RZ1along the substantially curved section 108 a of inner wall 108. In FIG.2, the enriched product stream comprising the substantially solidcomponent is directed to deflector 210, which deflects the enrichedproduct stream comprising the substantially solid component towardsreslurry zone RZ2. In FIG. 3, the enriched product stream comprising thesubstantially solids component is directed into chute 310 and then intoreslurry zone RZ3.

The enriched product stream comprising the substantially solid componentexiting from filtration zones FZ1, FZ2 or FZ3 primarily comprises thesubstantially solid component from the solid-liquid stream, but maycomprise small amounts of the substantially liquid component andimmiscible fluid. The amount of the substantially liquid componentpresent in the enriched product stream comprising the substantiallysolid component may be affected by such factors including, but notlimited to, the type and size of the substantially solid component inthe solid-liquid stream, the size of the pores in the filter, the flowrate of the solid-liquid stream injected into the filter column, and thetype and flow rate of the immiscible fluid. However, it is preferredthat the enriched product stream comprising the substantially solidcomponent comprise less than about 40 weight percent of thesubstantially liquid component, preferably less than about 35 weightpercent of the substantially liquid component, more preferably less thanabout 30 weight percent of the substantially liquid component, even morepreferably less than about 25 weight percent of the substantially liquidcomponent, even more preferably less than about 20 weight percent of thesubstantially liquid component, even more preferably less than about 15weight percent of the substantially liquid component, even morepreferably less than about 10 weight percent of the substantially liquidcomponent, and most preferably less than about 5 weight percent of thesubstantially liquid component for best results.

In addition, the present invention is directed to maintaining a densephase comprising a substantially solids containing packed bed throughoutthe solid-liquid separation process, by maintaining the higher pressurezone at a temperature lower than the melting point of at least onesubstantially solid component in the solid-liquid stream. For thepurposes of the present invention, the temperature of the higherpressure zone can be determined by determining the temperature of theenriched product stream comprising the substantially solid componentremoved from the filter column. Alternatively, the temperature can bedetermined by placing temperature indicators in strategic locationswithin the higher pressure zone.

FIGS. 4 a-d further provide a stepwise depiction of the start-up of theseparation process of this present invention, which provides for theformation of a substantially solids containing packed bed within thesubstantially hollow cavity 102, 202, or 302 of the filter column 101,201, or 301. In this embodiment, as shown in FIG. 4 a, the solid-liquidstream initially enters near the closed end 103, 203, or 303 of thesubstantially hollow cavity 102, 202, or 302 through one or moresolid-liquid stream inlets (not shown) and the immiscible fluid (notshown) initially enters the open end 104, 204, or 304 of thesubstantially hollow cavity. The immiscible fluid initially enters thesubstantially hollow cavity 102, 202, or 302 at a pressure sufficientfor at least a portion of the immiscible fluid to pass through at leastone filter 109, 209, or 309 to the lower pressure zone. The solid-liquidstream moves towards the substantially open end of the substantiallyhollow cavity 102, 202, or 302 by crossing at least one filter 109, 209,or 309 wherein at least a portion of the substantially liquid componentof the solid-liquid passes through at least one filter 109, 209, or 309forming a filtrate that exits the filter column through a bottom portion107, 207, or 307 of the filter tube 105, 205, or 305 that extendsthrough the closed end of the filter column. The opposing pressure ofthe immiscible fluid preferably prevents the solid-liquid stream fromcompletely crossing the filter 109, 209, or 309 on its way towards theopen end 104, 204, or 304 of the substantially hollow cavity 102, 202,or 302.

Referring now to FIG. 4 b, as the substantially liquid component of thesolid-liquid stream passes through the filter 109, 209, or 309, thesubstantially solid component begins to form a substantially solidscontaining packed bed 415 within the substantially hollow cavity 102,202, or 302. As the substantially solid component accumulates, thesubstantially solids containing packed bed increases in size, and mayfill the entire section between the filter and the wall, as shown inFIG. 4 c. Substantially solids containing packed bed 415 depicts theportion of the substantially solids containing packed bed wherein mainlyliquid flows towards the filter, while substantially solids containingpacked bed 416 depicts the portion of the dense phase wherein theimmiscible fluid flows towards the filter. Once the substantially solidcontaining packed bed 415 and 416 is formed, the pressure imparted bythe solid-liquid stream is generally greater than the pressure exertedby the immiscible fluid. As a result, as shown in FIG. 4 c, at least aportion of the substantially solids containing packed bed 415 and 416moves towards the substantially open end 104, 204, or 304 of thesubstantially hollow cavity 102, 202, or 302. When the separationprocess reaches steady-state, the amount of substantially solidscontaining packed bed leaving the top of the filter column 101, 201, or301, is equal to the deposition rate of solids at the bottom of thesubstantially solids containing packed bed. This is shown in FIG. 4 d.

The present invention provides for efficient separation of crystallizedproducts, such as paraxylene, from a solid-liquid stream at relativelylow temperatures without risk and attendant penalties associated withfreezing a wash liquid within the filter column and causing completefailure of the solid-liquid separation process.

The present invention also provides for a substantial reduction incapital expenditure and routine maintenance by reducing the number ofmoving parts required by solid-liquid separation process units, such asscreen bowl and pusher centrifuges. The filter column, according to thepresent invention, can comprise little or no moving parts, substantiallyreducing the routine maintenance costs associated with conventionalsolid-liquid separation units.

The present invention also provides for substantial savings inrefrigeration costs by allowing for solid-liquid separation ofcrystallization products under substantially isothermal conditions.Current solid-liquid processes, such as screen bowl centrifuges, addconsiderable amounts of energy to the process stream thereby raising thetemperature of the effluent streams. In a paraxylene crystallizationprocess, for example, this energy added to the process requiresincreased refrigeration costs.

The present invention also provides for a substantial cost savings byreducing the amount of solids lost in filtrate streams frequently foundin conventional solid-liquid separation processes and apparatuses.

The present invention also provides for the separation of substantiallyliquid components from substantially solids components in a filtercolumn at temperatures far below the melting point of crystals inslurries derived from a crystallization process that can be operated ina continuous manner without high loss of the crystals to the liquidfiltrate through one or more filters during the separation process.

The present invention also provides for the use of filter columns todebottleneck existing paraxylene units that already have centrifuges. Byadding filter columns and wash columns to an existing unit, it ispossible to increase the solids/liquid separation capacity while alsolowering the refrigeration requirement per pound of paraxylene product.Therefore, for existing units that have a refrigeration bottleneck orare limited by the capacity of the solids/liquid separation equipment,the proper installation of filter columns will provide a cost effectivedebottleneck.

The present invention also provides for filter columns to reducefeedstock losses to less valuable by-products by recovering moreparaxylene from the cold end solid liquid stream, thereby reducing theamount of paraxylene recycled to the isomerization reactor.

This invention has been described for the purposes of illustration onlyin connection with certain embodiments. However, it is recognized thatvarious changes, additions, improvements, and modifications to theillustrated embodiments may be made by those persons skilled in the art,all falling within the scope and spirit of the invention.

EXAMPLES

The following examples are presented to illustrate a process for therecovery and purification of paraxylene substantially in accordance withthe present invention and FIG. 3. The following parameters were measuredor calculated from measured variables. (1) the weight percent ofparaxylene in the solid-liquid stream; (2) the weight percent of solidsin the solid-liquid stream; (3) the temperature of the solid-liquidstream; (4) the weight percent of paraxylene in the filtrate; (5) theweight percent of solids in the filtrate; (6) the temperature of thefiltrate; (7) the weight percent of paraxylene in the cake; (8) theweight percent of liquid in the cake; and (9) the temperature of thecake. The temperature of the cake was not measured for the thirdexample.

Examples 1 and 2 utilized a filter column having an inside diameter of 6inches. The column contained a single filter tube approximately 29inches in length. The outside diameter of the filter tube was 2.375inches. The filter tube comprised a filter screen fabricated with a 316stainless steel CONIDUR® screen bought from Hein, Lehmann measuring 6.4inches in length. The top of the screen was located 5 inches from thetop of the filter tube and comprised 0.1 mm by 3 mm slits. The overallopen area of the screen was 9 percent.

For Example 1, the 6-inch diameter filter column was fed 1500 lb/hr of asolid-liquid stream comprising mixed xylenes from a commercial, lowtemperature crystallizer. The pressure of the solid-liquid streamcomprising mixed xylenes entering the filter column was approximately160 psia for this 30-hour test. Gaseous nitrogen was used as theimmiscible fluid. The temperature of the nitrogen was not controlled andtherefore varied with ambient temperature. The feed rate of the nitrogenwas 24 lb/hr and the inlet pressure was approximately 63 psia. Five setsof samples were removed during the 30-hour test, yielding the resultsshown in Table 1. TABLE 1 6″ Filter Column with 1500 lb/hr Solid-liquidstream and 24 lb/hr Nitrogen Sample 032-1 032-2 032-3 032-4 032-5 Hoursfrom Startup 3 6 20 24 30 Solid-liquid stream Wt % pX 25.9 26.0 25.826.4 26.3 Wt % solids 16.7 17.0 17.2 17.9 17.8 Temperature, ° F. −71.0−72.1 −74.5 −74.3 −74.4 Filtrate Wt % pX 11.1 10.8 10.7 10.3 10.4 Wt %solids 0.0 0.0 0.5 0.0 0.0 Temperature, ° F. −70.0 −70.5 −72.8 −72.8−72.6 Cake Wt % pX 87.2 85.5 85.4 85.7 86.5 Wt % liquid 14.4 16.2 16.316.0 15.0 Temperature, ° F. −68.0 −69.6 −57.1 −57.2 −54.8 NitrogenSupply Temperature, ° F. 82.2 82.5 73.4 81.0 86.9

For Example 2, the 6-inch diameter filter column was fed 1000 lb/hr of asolid-liquid stream comprising mixed xylenes from a commercial, lowtemperature crystallizer. The pressure of the solid-liquid streamcomprising mixed xylenes entering the filter column was approximately155 psia for this 54-hour test. Gaseous nitrogen was used as theimmiscible fluid. The temperature of the nitrogen was not controlled andtherefore varied with ambient temperature. The feed rate of the nitrogenwas 20 lb/hr and the inlet pressure was approximately 59 psia. Six setsof samples were removed during the 54-hour test, yielding the resultsshown in Table 2. TABLE 2 6″ Filter Column with 1000 lb/hr Solid-liquidstream and 20 lb/hr Nitrogen Sample 034-1 034-2 034-3 034-4 034-5 034-6Hours from Startup 3 6 21 30 45 53 Solid-liquid stream Wt % pX 23.9 24.024.8 26.3 26.6 26.6 Wt % solids 15.4 15.3 16.5 17.7 18.6 18.5Temperature, ° F. −75.7 −75.0 −76.1 −73.8 −76.6 −76.1 Filtrate Wt % pX10.3 10.3 10.4 10.6 10.5 10.1 Wt % solids 0.2 0.1 0.5 0.1 0.7 0.2Temperature, ° F. −73.7 −73.0 −73.9 −71.9 −74.5 −73.9 Cake Wt % pX 86.986.0 85.7 86.9 86.8 86.1 Wt % liquid 14.5 15.6 15.9 14.6 14.7 15.4Temperature, ° F. −72.1 −71.9 −69.5 −68.3 −68.7 −70.6 Nitrogen SupplyTemperature, ° F. 85.9 87.2 71.3 88.6 66.3 78.0

The third example utilized a filter column having an inside diameter of22.6 inches. The column contained 19 filter tubes approximately 48inches in length. These filter tubes were fabricated in the same manneras the filter tube installed in the 6-inch filter column as discussedabove.

For Example 3, the filter column was fed 10,000 lb/hr of a solid-liquidstream comprising mixed xylenes from a commercial, low temperaturecrystallizer. The pressure of the solid-liquid stream comprising mixedxylenes entering the filter column was approximately 90 psia for thefirst 30 hours of the test when the first three sets of samples wereremoved. The conditions of the crystallizer from which the solid-liquidstream was obtained were then changed. After waiting about 20 hours toallow the system to reach steady-state, three more sets of samples wereremoved over a 6 hour period. The pressure of the solid-liquid streamcomprising mixed xylenes feed entering the filter column wasapproximately 117 psia for these last sets of samples. Gaseous nitrogenwas used as the immiscible fluid. The temperature of the nitrogen wasnot controlled and therefore varied with ambient temperature. The feedrate of the nitrogen was 150 lb/hr and the inlet pressure wasapproximately 57 psia for the first 30 hours and approximately 72 psiafor the last three sets of samples. In all, six sets of samples wereremoved during the test, yielding the results shown in Table 3. TABLE 322.6″ Filter Column with 10,000 lb/hr Solid-liquid stream and 150 lb/hrNitrogen Sample 006-1 006-2 006-3 006-4 006-5 006-6 Hours from Startup 524 27 45 48 51 Solid-liquid stream Wt % pX 26.1 26.0 26.2 23.6 23.5 23.6Wt % solids 17.8 18.0 18.5 15.3 15.1 14.9 Temperature, ° F. −75.5 −77.2−78.3 −76.8 −76.4 −74.8 Filtrate Wt % pX 9.8 9.6 9.2 9.8 9.9 10.1 Wt %solids 0.0 0.0 0.0 0.0 0.0 0.0 Temperature, ° F. −74.3 −76.3 −77.4 −75.2−75.3 −73.8 Cake Wt % pX 83.5 84.3 86.5 85.1 86.0 85.7 Wt % liquid 18.317.4 15.0 16.5 15.5 16.0 Temperature, ° F. Not measured Nitrogen SupplyTemperature, ° F. 55.9 49.2 56.2 44.1 49.7 54.3

For Example 4, the 6 inch filter column was fed a mixed xylenes streamfrom a commercial slurry drum operating at about 25° F. The filtercolumn was operated over a wide range of process conditions. Gaseousnitrogen was used as the immiscible fluid. The temperature of thenitrogen was not controlled and therefore varied with ambienttemperature. Ten sets of samples were removed during this fifty-hourtest yielding the results shown in Table 4. TABLE 4 6″ Filter Columnwith Warm Solid-Liquid Stream Sample 025-1 025-2 025-3 025-4 025-5 025-6025-7 025-8 025-9 025.10 Hours from Startup 3 5 7 22 25 28 31 46 48 50Solid-liquid stream Rate, lb/hr 3500 3500 3500 3500 2500 3000 3950 32252851 2950 Wt % pX 78.0 76.3 76.1 77.2 77.6 78.8 77.5 73.8 69.2 70.4 Wt %solids 41.1 34.4 35.6 40.6 41.0 40.2 40.0 29.0 13.9 18.4 Temperature, °F. 23.8 24.0 23.4 23.7 23.2 25.7 24.7 24.0 25.8 24.9 Pressure, psig 8991 72 84 88 82 80 68 51 56 Filtrate Wt % pX 63.0 64.5 62.7 61.2 62.063.9 62.1 63.5 64.6 64.2 Wt % solids 1.0 1.6 0.0 0.0 0.0 0.0 0.0 1.0 1.21.2 Temperature, ° F. 25.8 24.7 22.7 23.1 22.7 25.0 23.9 23.6 25.4 24.6Wt % pX 92.9 93.5 92.5 92.4 93.7 93.1 92.4 92.9 94.5 93.6 Wt % liquid19.0 17.9 20.2 19.8 16.5 19.6 20.2 19.1 15.3 17.7 Temperature, ° F. 23.623.6 23.3 23.2 22.7 25.0 24.3 23.8 25.1 24.4 Nitrogen Supply Rate, lb/hr4.5 6.5 2.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Temperature, ° F. 76.1 78.6 80.375.9 80.1 85.4 86.1 78.1 78.2 82.6 Pressure, psig 35 35 32 34 33 32 3431 28 29

These four examples illustrate a number of important points. Thisinvention can be built at various sizes and can operate successfullywith a variety of solid-liquid stream rates and immiscible fluid rates.In all cases presented in the tables, very little solids were observedin the filtrate. The paraxylene in the filtrate was primarily derivedfrom the liquid paraxylene present in the solid-liquid stream. Ingeneral, the filtrate temperature was only about 1 to 2° F. warmer thanthe solid-liquid stream despite the fact the temperature of the nitrogensupply was 120 to 160° F. warmer than the solid-liquid stream. Keepingthe filtrate temperature close to the solid-liquid stream temperatureprovides savings in refrigeration costs. It is possible for thetemperature of the cake near the top of the filter column to besubstantially warmer than the solid-liquid stream and yet still observea filtrate temperature close to the temperature of the solid-liquidstream. This is illustrated in Table 1. It is also possible to operatethe invention so that the cake near the top of the filter column is muchcloser to the temperature of the solid-liquid stream as shown in Table2. Finally, changes in the operation of the upstream crystallizer canaffect the required inlet pressures to the filter column but leave theoverall sample results substantially unaffected. This is shown in Table3.

The data in Table 4 can be grouped in several ways to demonstrate thechanges in filter column performance to changes in process conditions.The first four sets of samples were taken at substantially the same feedconditions but at various immiscible gas rates. The column pressuresincrease with gas rate. At 2.5 lb/hr of gas, the solid-liquid feedpressure is 72 psig and the inlet gas pressure is 32 psig. At 6.5 lb/hrof gas, these pressures are 91 and 35 psig, respectively. The cakesamples indicate that wetter cake is obtained at lower gas rates. Adifferent grouping of the data presented in Table 4 demonstrates theeffect of varying solid-liquid feed rates holding the other variablessubstantially constant. This comparison involves samples 025-1 and 025-4through 025-7. Finally, the last grouping involves samples 025-1, 025-4,and 025-8 through 025-10 in which the intent was to demonstrate theeffect of varying the solids content of the feed holding all othervariables substantially constant. These results, particularly whencombined with the results presented in Tables 1 and 2 wherein the sameequipment was used to obtain data at significantly different conditions,clearly demonstrate that this invention can operate successfully over awide range of operating conditions.

1. A filter column apparatus comprising a filtration zone and asubstantially enclosed reslurry zone, wherein said filtration zone andsaid substantially enclosed reslurry zones are separated by a barrierwall.
 2. The apparatus of claim 1 wherein said filtration zone isannularly disposed around said substantially enclosed reslurry zone. 3.The apparatus of claim 1 wherein said substantially enclosed reslurryzone defines a substantially central axis and said filtration zone alsodefines a substantially central axis, and wherein said substantiallycentral axes are in substantial proximity to each other.
 4. Theapparatus of claim 1 wherein said filtration zone comprises at least onefilter tube.
 5. The apparatus of claim 1 wherein said filtration zonecomprises at least one filter.
 6. The apparatus of claim 1 wherein saidbarrier wall has thermal insulation properties.
 7. The apparatus ofclaim 1 wherein said reslurry zone comprises a straining means to assistwith reslurry operations within said reslurry zone.
 8. A filter columnapparatus comprising a substantially enclosed filtration zone and areslurry zone, wherein said substantially enclosed filtration zone andsaid reslurry zone are separated by a barrier wall.
 9. The apparatus ofclaim 8 wherein said reslurry zone is annularly disposed around saidsubstantially enclosed filtration zone.
 10. The apparatus of claim 8wherein said reslurry zone defines a substantially central axis and saidsubstantially enclosed filtration zone also defines a substantiallycentral axis, and wherein said substantially central axes are insubstantial proximity to each other.
 11. The apparatus of claim 8wherein said filtration zone comprises at least one filter tube.
 12. Theapparatus of claim 8 wherein said filtration zone comprises at least onefilter.
 13. The apparatus of claim 8 wherein said filter column furthercomprises a deflector means to direct at least one substantially solidcomponent into said reslurry zone.
 14. The apparatus of claim 8 whereinsaid barrier wall has thermal insulation properties.
 15. The apparatusof claim 8 wherein said reslurry zone comprises a straining means toassist with reslurry operations within said reslurry zone.
 16. A filtercolumn apparatus comprising a filtration zone, wherein said filtercolumn is in substantial cooperation with a reslurry zone.
 17. Theapparatus of claim 16 wherein said reslurry zone is situated in a chuteand wherein said filtration zone is situated in a filter column definedaround a substantially central axis.
 18. The apparatus of claim 16wherein said filtration zone comprises at least one filter tube.
 19. Theapparatus of claim 16 wherein said filtration zone comprises at leastone filter.
 20. The apparatus of claim 17 wherein said chute optionallycomprises a straining means to assist with reslurry operations withinsaid reslurry zone.
 21. A process for separating at least a portion ofone or more substantially solid components from a solid-liquid streamcomprising said one or more substantially solid components and one ormore substantially liquid components, said process comprising: a.contacting an immiscible fluid with one or both of at least a portion ofsaid solid-liquid stream, or at least a portion of said one or moresubstantially solid components; and b. passing at least a portion ofsaid one or more substantially liquid components and at least a portionof said immiscible fluid through at least one filter and forming afiltrate comprising said substantially liquid component and saidimmiscible fluid, thus leaving an enriched product stream comprisingsaid one or more substantially solid components.
 22. The process ofclaim 21 wherein said contacting and passing steps substantially occurin a filtration zone comprising said at least one filter, an area ofhigher concentration of said one or more substantially solid components,an area of lower concentration of said one or more substantially solidcomponents.
 23. The process of claim 22 wherein said area of higherconcentration of said one or more substantially solid components islocated around or outside of said at least one filter, and wherein saidarea of lower concentration of said one or more substantially solidcomponents is located within or inside of said at least one filter. 24.The process of claim 22 wherein said contacting step occurssubstantially in said area of higher concentration of said one or moresubstantially solid components.
 25. The process of claim 21 wherein saidcontacting of step a occurs in a substantially countercurrent flow. 26.The process of claim 21 wherein said contacting and passing stepssubstantially occur in a filtration zone comprising said at least onefilter, a higher pressure zone, an a lower pressure zone.
 27. Theprocess of claim 26 wherein said higher pressure zone is located aroundor outside of said at least one filter, and wherein said lower pressurezone is located within or inside of said at least one filter.
 28. Theprocess of claim 27 wherein said higher pressure zone is maintained at atemperature lower than the melting point of said one or moresubstantially solid components in said solid-liquid stream.
 29. Theprocess of claim 26 wherein said contacting step occurs in said higherpressure zone.
 30. The process of claim 21, wherein said solid-liquidstream comprises at least one hydrocarbon selected from the groupconsisting of ethylbenzene, paraxylene, metaxylene, orthoxylene,benzene, toluene, paraffins, and naphthenes, or combinations thereof.31. The process of claim 21 wherein at least a portion of saidsolid-liquid stream is the direct or indirect product or byproduct of atoluene disproportionation process.
 32. The process of claim 21 whereinat least a portion of said solid-liquid stream is the direct or indirectproduct or byproduct of a crystallization process.
 33. The process ofclaim 32 wherein said crystallization process comprises at least oneslurry section.
 34. The process of claim 21 wherein at least a portionof said solid-liquid stream is the direct or indirect product orbyproduct of a molecular sieve adsorption process.
 35. The process ofclaim 21 wherein said filtrate comprises at least one hydrocarbonselected from the group consisting of ethylbenzene, paraxylene,metaxylene, orthoxylene, benzene, toluene, paraffins, and naphthenes, orcombinations thereof.
 36. The process of claim 21, wherein saidimmiscible fluid is selected from the group consisting of nitrogen,carbon dioxide, hydrogen, compressed air, xenon, argon, neon, helium,methane, ethane, natural gas, and steam.
 37. The process of claim 22wherein said area of higher concentration of said one or moresubstantially solid components comprises a dense phase comprising asubstantially packed bed of said one or more substantially solidcomponents.
 38. The process of claim 21, wherein at least a portion ofsaid enriched product stream comprising said one or more substantiallysolid components is directed to a reslurry zone.
 39. The process ofclaim 38 wherein at least a portion of said enriched product stream isreslurried with a flush feed in said reslurry zone.
 40. The process ofclaim 21 wherein at least a portion of said one or more substantiallyliquid components is optionally recycled back to said solid-liquidstream.
 41. The process of claim 21 wherein said solid-liquid streamcomprises between about 0.5 weight percent to about 65 weight percent ofsaid substantially solid components.
 42. The process of claim 21 whereinsaid solid-liquid stream comprises between about 5 weight percent toabout 60 weight percent of said substantially solid components.
 43. Theprocess of claim 21 wherein said solid-liquid stream comprises betweenabout 10 weight percent to about 55 weight percent of said substantiallysolid components.
 44. A packed bed process for separating at least aportion of at least one substantially solid component from asolid-liquid stream comprising said at least one substantially solidcomponent and at least one substantially liquid component, said processcomprising the steps of: a. applying an immiscible fluid for assistingformation of a substantially solids containing packed bed defining a bedvoid space; and b. passing at least a portion of said at least onesubstantially liquid component through said void space of saidsubstantially solids containing packed bed, thus leaving an enrichedproduct stream comprising said at least one substantially solidcomponent.
 45. The process of claim 44 wherein at least a portion ofsaid at least one substantially liquid component passes through at leastone filter.
 46. The process of claim 45 wherein the area around oroutside of said at least one filter comprises a higher pressure zone.47. The process of claim 45 wherein the area within or inside of said atleast one filter comprises a lower pressure zone.
 48. The process ofclaim 46 wherein said solid-liquid stream and said immiscible fluid aredirected into said higher pressure zone.
 49. The process of claim 44wherein said immiscible fluid applies an opposing pressure to saidsubstantially solids containing packed bed.
 50. The process of claim 46,wherein said higher pressure zone is maintained at a temperature lowerthan the melting point of said at least one substantially solidcomponent in said solid-liquid stream.
 51. The process of claim 44wherein at least a portion of said solid-liquid stream is the direct orindirect product or byproduct of a toluene disproportionation process.52. The process of claim 44 wherein at least a portion of saidsolid-liquid stream is the direct or indirect product or byproduct of acrystallization process.
 53. The process of claim 52 wherein saidcrystallization process comprises at least one slurry section.
 54. Theprocess of claim 44 wherein at least a portion of said solid-liquidstream is the direct or indirect product or byproduct of a molecularsieve adsorption process.
 55. The process of claim 45 wherein said atleast a portion of said substantially solids containing packed bed is insubstantial cooperation with said at least one filter.
 56. The processof claim 44 wherein at least a portion of said immiscible fluid passesthrough at least a portion of said substantially solids containingpacked bed.
 57. The process of claim 45 wherein at least a portion ofsaid immiscible fluid passes through said at least one filter.
 58. Theprocess of claim 44 wherein at least a portion of said at least onesubstantially solid component of said solid-liquid stream forms aportion of said substantially solids containing packed bed.
 59. Theprocess of claim 44 wherein at least a portion of said substantiallysolids containing packed bed is removed as said enriched product streamcomprising said at least one substantially solid component.
 60. Theprocess of claim 59 wherein at least a portion of said substantiallysolid component of said substantially solids containing packed bed movesin a substantially constant direction for displacement as said enrichedproduct stream comprising said at least one substantially solidcomponent.
 61. The process of claim 44 wherein said immiscible fluidapplies a pressure substantially opposing the direction of displacementof said substantially solids containing packed bed.
 62. A start upprocess for forming a substantially solids containing packed bed, saidprocess comprising: a. contacting a solid-liquid stream comprising atleast one substantially solid component and at least one substantiallyliquid component with an immiscible fluid, b. directing at least aportion of said at least one substantially liquid component through atleast one filter to form said substantially solids containing packedbed, wherein said bed further defines a bed void space; and c. passingat least a portion of said at least one substantially liquid componentthrough said bed void space of substantially solids containing packedbed.
 63. The process of claim 62 wherein at least a portion of saidimmiscible fluid passes through at least a portion of said substantiallysolids containing packed bed.
 64. The process of claim 62 wherein atleast a portion of said immiscible fluid passes through said at leastone filter.
 65. The process of claim 62 wherein at least a portion ofsaid at least one substantially solid component of said solid-liquidstream forms a portion of said substantially solids containing packedbed.
 66. The process of claim 62 wherein said immiscible fluid applies apressure substantially opposing the direction of displacement of saidsubstantially solids containing packed bed.
 67. A process for separatingat least a portion of substantially solid paraxylene from a solid-liquidstream comprising said substantially solid paraxylene and asubstantially liquid aromatic stream, said process comprising: a.contacting an immiscible fluid with one or both of said solid-liquidstream, or at least a portion of said substantially solid paraxylene;and b. passing at least a portion of said substantially liquid aromaticstream, and at least a portion of said immiscible fluid through at leastone filter and forming a filtrate comprising said substantially liquidaromatic stream and said immiscible fluid, thus leaving an enrichedproduct stream comprising said substantially solid paraxylene c.reslurrying said enriched product stream with a flush feed.
 68. Theprocess of claim 67 wherein said contacting and passing stepssubstantially occur in a filtration zone comprising said at least onefilter, an area of higher concentration of said substantially solidparaxylene, an area of lower concentration of substantially solidparaxylene.
 69. The process of claim 68 wherein said area of higherconcentration of said substantially solid paraxylene is located aroundor outside of said at least one filter, and wherein said area of lowerconcentration of said substantially solid paraxylene is located withinor inside of said at least one filter.
 70. The process of claim 68wherein said contacting step occurs substantially in said area of higherconcentration of said substantially solid paraxylene.
 71. The process ofclaim 67 wherein said contacting of step a. occurs in a substantiallycountercurrent flow.
 72. The process of claim 67 wherein said contactingand passing steps substantially occur in a filtration zone comprisingsaid at least one filter, a higher pressure zone, an a lower pressurezone.
 73. The process of claim 72 wherein said higher pressure zone islocated around or outside of said at least one filter, and wherein saidlower pressure zone is located within or inside of said at least onefilter.
 74. The process of claim 72 wherein said contacting step occursin said higher pressure zone.
 75. The process of claim 67, wherein saidsolid-liquid stream comprises at least one hydrocarbon selected from thegroup consisting of ethylbenzene, paraxylene, metaxylene, orthoxylene,benzene, toluene, paraffins, and naphthenes, or combinations thereof.76. The process of claim 62 wherein said solid-liquid stream comprisesbetween about 0.5 weight percent and 65 weight percent of saidsubstantially solid paraxylene.
 77. The process of claim 62 wherein saidsolid-liquid stream comprises between about 5 weight percent and 60weight percent of said substantially solid paraxylene.
 78. The processof claim 62 wherein said solid-liquid stream comprises between about 10weight percent and 55 weight percent of said substantially solidparaxylene.
 79. The process of claim 62, wherein said immiscible fluidis selected from the group consisting of nitrogen, carbon dioxide,hydrogen, compressed air, xenon, argon, neon, helium, methane, ethane,natural gas, and steam.